Development and kinetic evaluation of a low-cost temperature-sensitive shape memory polymer for 4-dimensional printing

4D printing has been evolving from traditional 3D printing in the past years as an enabling technology imparting additive manufacturing with unprecedented functionality of creating time-dependent geometries. However, the current development status presents both cost and technical barriers, keeping 4D printing from being accessible to the general 3D printer users, in particular those who already have traditional 3D printing machines. This paper reported the development and kinetic evaluation of a low-cost temperature-sensitive shape memory polymer for 4D printing. The shape memory polymer is made of polylactic acid (PLA)-thermoplastic polyurethane (TPU) composite in the form of filaments under different weight concentration ratios through extrusion processes. The filaments were tested in an FDM process to make 4D printed structures. The experiment study reveals the relationship between the material concentration ratio, recovery rate of sample workpieces, and the number of repeating recovery cycles. In addition, dynamic characteristics such as recovery velocity, acceleration, angular velocity, and angular acceleration were also investigated to characterize the behavior of the shape memory polymer. At the end of the paper, examples are provided to demonstrate the capability of the shape memory polymer in FDM-based 4D printing applications.